Fears that cloning caused Dolly the Sheep to have early-onset osteoarthritis are 'unfounded', according to new research.

Dolly, the first mammal to be cloned from an adult cell, remains controversial some 21 years after her birth. Her death at the age of almost six, a year after she developed osteoarthritis, was thought to be evidence that cloned animals age prematurely compared with animals conceived naturally. Now, scientists at the Universities of Nottingham, Glasgow and Bristol and the National Museums Scotland in Edinburgh where Dolly's taxidermied body is on display, have shown that cloned sheep, including Dolly, appear to age at the same rate as non-cloned sheep.

After studying sheep cloned from the same cells as Dolly (known as the Nottingham Dollies) and finding that they aged normally in a study published in Nature Communications in 2016, the team wanted to understand why Dolly appeared to have aged differently.

'Our findings of last year appeared to be at odds with original concerns surrounding the nature and extent of osteoarthritis in Dolly – who was perceived to have aged prematurely,' said study author Professor Kevin Sinclair at the University of Nottingham.'Yet no formal, comprehensive assessment of osteoarthritis in Dolly was ever undertaken. We therefore felt it necessary to set the record straight.'

In the latest study, the researchers took X-ray images of the skeletons of Dolly, her naturally conceived daughter Bonnie, and Megan and Morag - two sheep who were born the year before Dolly and were the first animals to be successfully cloned from differentiated cells. Three veterinary surgeons scored each skeleton for the presence and severity of osteoarthritis. The results were compared with those of sheep cloned from the same cells as Dolly, and to those of naturally conceived sheep.

Professor Sandra Corr at the University of Glasgow, a study author, said: 'We found that the prevalence and distribution of radiographic osteoarthritis was similar to that observed in naturally conceived sheep, and our healthy aged cloned sheep. As a result we conclude that the original concerns that cloning had caused early-onset osteoarthritis in Dolly were unfounded.'

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